Conventional displays produce white background illumination either by a cold cathode tube, white light-emitting diodes or by a combination of red, green and blue light-emitting diodes. Because of their fast turn-on time, backlights with light-emitting diodes allow control of the brightness by means of pulse modulation. Such LED backlights will be considered further here.
For a subjective increase of contrast, the LED backlighting of a display is typically subdivided into segments, each with its own driving and thus its own brightness control. The task of determining the brightness is taken on here by a digital video processor. The segments are conventionally driven by means of pulse-modulated signals that are generated independently of one another. This leads to intermodulation interference on the display, which is visible to the observer in the form of stripes.